In the related art, for bending and stretching of joints of robot hands or robot arms, rotary drive of a drive source is transmitted by various driving mechanisms such as a gear mechanism or a wire motion mechanism. The gear mechanism has problems such as low controllability due to backrush of gears and size or weight increases due to the presence of gear trains, while the wire motion mechanism has problems such as low controllability due to the necessity of adjustment of wire tension and probability of wire elongation, and increases in number of parts and size due to the necessity of a mechanism for rotating the wire.
As countermeasures for these problems, a three-dimensional cam mechanism is proposed. The three-dimensional cam mechanism includes a cam rotary shaft coupled to a motor shaft and supported by a supporting member, and is configured to convert a rotary motion of a three-dimensional cam into a swinging motion of a driven-side link by the driven-side link supported by the above-described supporting member being guided by a cam guiding surface of the three-dimensional cam rotating about the cam rotary shaft. Accordingly, with a flexible design of a shape of the cam guiding surface, a smooth swinging motion of the driven-side link is achieved without causing backrush as in the gear mechanism (see PTL 1; Japanese Patent No. 4448554, PTL 2; Japanese Patent No. 4388566).